Crawl space mold inspection: what to check, and who to call

How to test for mold in a crawl space

Look first. A flashlight inspection of the joists, the underside of the subfloor, the sill where the floor framing meets the foundation, and any insulation between the joists shows what a lab sample would only name. EPA's position: “In most cases, if visible mold growth is present, sampling is unnecessary.” CDC's is shorter: “CDC does not recommend mold testing.”

What a useful inspection writes down instead:

• The extent, in square feet, and which framing members it is on.
• The moisture source: standing water, wet soil, a plumbing leak, or damp air from vents.
• The condition of the wood under the growth, and of any insulation that is wet or sagging.
• Photos with locations, so a second company can quote the same work.

Sources: EPA, A Brief Guide to Mold, Moisture and Your Home; CDC, Mold. When testing does earn its fee: mold testing, and when you need it.

Where crawl space moisture comes from

Most of it comes up from the soil. EPA's moisture guidance for building design lists “exposed earth in crawl spaces or basements” among the sources of indoor humidity, and says that “damp basements or crawlspaces may add as much water vapor to the air in a day as all the other internal sources combined.” The same document describes the two ways crawl spaces are built: “Crawl space foundations may be vented to the outdoors or air sealed.” For both designs it describes a plastic or elastomeric membrane over the soil to “prevent evaporation from the soil into the crawl space.”

For the living space above, EPA's household target is to “keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity.” A hygrometer, a small humidity gauge, left in the crawl space for a few days shows whether the air down there is the problem.

Cleaning without fixing the source is a repeat purchase. In EPA's words: “If you clean up the mold, but don't fix the water problem, then, most likely, the mold problem will come back.”

Sources: EPA, Moisture Control Guidance for Building Design, Construction and Maintenance (Dec 2013); EPA, A Brief Guide to Mold, Moisture and Your Home.

How serious is mold in a crawl space?

Size and cause decide it. EPA's line for doing it yourself is about 10 square feet: “If the moldy area is less than about 10 square feet (less than roughly a 3 ft. by 3 ft. patch), in most cases, you can handle the job yourself.” Past that, or after a lot of water damage, EPA refers readers to its guide for professional remediation. Growth that returns after cleaning, wood that is soft under the mold, or a crawl space that floods are signs the moisture problem is bigger than the patch. Our page on whether you need mold remediation walks through the EPA line in detail.

Source: EPA, Mold Cleanup in Your Home.

Will insurance cover mold in a crawl space?

It depends on what caused it. The Texas Department of Insurance summarises the usual policy language: “Most homeowner and renters policies cover sudden and accidental water damage,” and “Most home policies don't cover water damage from gradual leaks or seepage, and that includes damage from mold.” Mold from a pipe that burst under the floor is a different claim from mold that grew over years of damp soil. Read your own policy, and call your insurer before any permanent repair.

Source: Texas Department of Insurance, When are water damage and mold covered by insurance?

One company or two?

Texas writes the conflict of interest into law: “A license holder may not perform both mold assessment and mold remediation on the same project.” New York Labor Law §936 does the same. In other states nothing stops the company that inspects from quoting the removal, so ask. In Texas and New York, check the license of whoever does either job.

Source: Tex. Occ. Code § 1958.155. What inspections and removal cost, crawl space included: mold remediation cost by scope.

Common questions